JPH03195567A - Processing method for carbon tetrachloride - Google Patents

Abstract

PURPOSE:To convert carbon tetrachloride into an economically useful material by reacting methanol and carbon tetrachloride in the gas phase with a catalyst carried with a halogenide or an oxide of a specific element on activated carbon. CONSTITUTION:For the processing method for carbon tetrachloride, methanol and carbon tetrachloride are reacted in the gas phase with a catalyst carried with a halogenide or an oxide of at least one kind of element among the groups IB, IIA, IIB, IVB, VIIB, VIII of the periodic table on activated carbon under the coexistence of hydrogen chloride as required. Carbon tetrashloride 95% or above is reacted with methanol at a relatively low temperature (150-200 deg.C) in a short time (10-20 sec), and almost all methanol can be converted into useful methyl chloride.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a treatment method for rendering carbon tetrachloride harmless, which is considered to be one of the causes of ozone layer depletion.

(Prior art and its problems) In recent years, the destruction of the earth's ozone layer due to chemical substances such as specific fluorocarbons has become a major social problem.

Resolutions have been made both domestically and internationally to completely abolish this specific fluorocarbon by the end of this century, and plans are being made in the industrial world to follow the same. However, in terms of ozone destruction ability, there are substances other than specific fluorocarbons that have comparable ability, and carbon tetrachloride (CC1,) is one of them. While Freon-11 and -12 each have an ozone depletion coefficient of 1.0, carbon tetrachloride has an ozone depletion coefficient of 1.0 to 1.2, which is equivalent to or higher than that. In addition to its ability to destroy ozone, carbon tetrachloride is also considered one of the causes of global warming.

Therefore, similar to fluorocarbons, carbon tetrachloride has become a trend both domestically and internationally to be completely abolished by the end of this century.

The industrial method for producing carbon tetrachloride is: ■ Carbon disulfide method: CS2+ 3 C1□-1→CCV4+52C1□■ Chlorination method of methane or methyl chloride: CH, + 4 Cl
2CCL + 4 HClCH3Cl+3 C12-1 → CCl4+3HC1. The former method selectively produces carbon tetrachloride, so even if production is discontinued,
The impact on other areas is small. However, the latter is not a method for selectively obtaining carbon tetrachloride. That is, CH2CH2
CH, C1+I■CI CI(, Cl + C"2-CH□C1□+HCICI
(, Cl □ 1 □ - 1 → CHCl, + HCICI (C
]3 + C1□□-CC] 4 + HC1, CI-(4→CH, Cl→CH2Cl□→C
This is a sequential simultaneous chlorination method in which CCl4 is finally produced via HCL, and the product is a mixture of unreacted methane and chloromethanes ranging from methyl chloride to carbon tetrachloride.

These intermediate chlorinated products of methane have a large market where they are useful, so if this production method is discontinued, it will have an extremely large impact on other products. That'2 CHJ
In order to obtain C1, CH2-C1, or CHC1, the by-product of carbon tetrachloride (CCI4) is unavoidable due to the characteristics of this reaction mechanism.

Therefore, a means for quickly converting by-product carbon tetrachloride into other harmless useful substances is desired. The following methods are currently under research and development and have already been industrialized.

i) Reduction of carbon tetrachloride with hydrogen to less chlorinated methane: CCI, +H2 uni: 7keno' CHCl,, CH2
Cl.

This method has a slow reaction rate and a limited catalyst life.
In addition, there are problems such as a large amount of impurities such as ClCH2CH2C1 being produced as by-products, and the method has not yet reached the level of a laboratory.

it) High-temperature combustion: This is a method in which methane, LPG, etc. are burned together and recovered as carbon dioxide and hydrogen chloride. It burns at a high temperature of 1,000 degrees Celsius, and requires a specially constructed furnace using bricks or the like as the furnace material. Furthermore, the carbon dioxide and hydrogen chloride obtained by recovery have low added value and can be obtained in large quantities at low cost using other methods.

In addition to direct chlorination of methane, a reaction between methanol and hydrogen chloride is known as an industrial method for producing methyl chloride (CH3C1). Since the reaction rate of this reaction is slow in the liquid phase, it is difficult to increase the utilization rate of both raw materials, but it is possible under a gas phase catalyst.

This gas phase catalyst includes A1□O3, pumice, kaolin,
IB group (C
11), ■Δ group (Mg, Ca, Ba), II B group (z"1, Cd, Hg), VIB group (Cr, Mo)
Catalysts are known in which halides or oxides of elements of Group 1B (Mn) and Group 2 (Fe, Co, Ni) are supported.

In the case of just the esterification reaction of methanol, there is no extreme difference in the catalytic ability of the above two, but in the reaction of methanol and carbon tetrachloride, it is assumed that the hydrolysis reaction of carbon tetrachloride proceeds, and in the past There is no example of high-yield, high-speed conversion to methyl chloride.

Also, JP-A-56-167628 and JP-A No. 57-16
Publication No. 5330 has a description of reacting hydrogen chloride gas containing CH2-C1□, CHCl, and CCl4 with methanol using a ZnCl2-supported Al2O catalyst system.
These products aim to obtain CH3-C1 by directly reacting hydrogen chloride immediately after leaving the chlorination reactor with methanol without separating hydrogen chloride from the gas containing chloromethane, which is the product. Therefore, it is assumed that one of the accompanying products, CH2Cl□, CHCl3, and CCl4, does not decompose.

(Product chloromethane) The technology described in JP-A-56-167628 uses CHCl
3. Z n Cl□/Al□0. Carbon precipitation due to decomposition of CCl4 is a reaction catalyst between methanol and hydrogen chloride. The purpose is to prevent the inactivation of
No. 330 shows in its examples that entrained CH2Cl□, CHCl, and CCl4 are not decomposed at all with the Zn'C1□/Al□03 catalyst.

(Problems to be Solved by the Invention) An object of the present invention is to provide a method for converting carbon tetrachloride into an economically useful substance by reacting it with methanol in high yield and at high speed.

(Means for Solving the Problems) The method for treating carbon tetrachloride according to the present invention is based on IB of the periodic table.
A halide or oxide of at least one element from Group IIA, Group IIB, Group VIB, Group 1B, Group 2, optionally in the coexistence of hydrogen chloride.

This method is characterized by reacting methanol and carbon tetrachloride in the gas phase using a catalyst supported on activated carbon.

This invention is shown in a comprehensive reaction formula as follows: 4, CH, ○I (+CC14)4CH, C1+2H20
+C○, =・(1), but this unreacted portion is CCI, +2I-I20-)CO2+4HC1...
...(2) (hydrolysis reaction of carbon tetrachloride) 4CII, ○H+4HC1-→4CH, C1+2H20
...(3) (Esterification reaction of methanol)

To explain this in more detail, the catalysts used in the present invention include group IB (Cu) of the periodic table, group nA (Mg
, Ca, Ba), Group IIB (Zn, Cd, Hg),
Activated carbon supports halides or oxides of metals from Group VIB (Cr, Mo), Group ■B (M n ), Group II (Fe, Co, Ni), but there is no reaction within them. Preferred are halides or oxides of metals of Group 1, which have high kinetics, especially zinc chloride.

In the present invention, by using activated carbon as a carrier, unreacted (2), which dominates the rate of the above-mentioned overall reaction (1), is significantly promoted, and methanol and carbon tetrachloride are produced in high yield and at a high rate. It became possible to react with

The difference in reaction rate depending on the type of carrier is due to the specific surface area, as shown in the table below.

Type of carrier Specific surface area (resistance 72) Activated carbon 7
00~1,500 Alumina 150~350 Silica 200~60
0 Activated clay 100-250 Synthetic zeolite 400-750 Activated carbon has a larger specific surface area than other carriers and provides a large area of active surface for reactants.

This reaction starts at about 150°C, but preferably up to about 250°C. The reaction rate increases further at higher temperatures, but 25
If the temperature exceeds 0°C, corrosivity increases and it becomes difficult to select a permanent material. If the reaction pressure is increased, the volume can be reduced accordingly, but it becomes difficult to select a permanent material due to its strength considering corrosion, and in the end, it is reduced from atmospheric pressure to 5 kg/a+? Preferably up to G position. Under the above conditions, the residence time is 10-20
In seconds, more than 95% of carbon tetrachloride reacts with methanol, and almost all of it is converted to methyl chloride.

When considering an industrial process, simultaneous addition of an excess of methanol and a commensurate amount of hydrogen chloride is preferred. In a methane or methyl chloride chlorination plant that produces carbon tetrachloride as a by-product, it is economically advantageous to add a step in which hydrogen chloride, a by-product of the reaction, is reacted with methanol and converted to methyl chloride. If the present invention is carried out in the same reactor, it becomes possible to produce chloromethane without emitting harmful carbon tetrachloride. The raw material ratio at that time is preferably as follows. Here, if the molar ratio is less than 1.01, the amount of unreacted methanol increases and [2CI-I30H-→(C
H3)20+H20] dimethyl ether increases due to the side reaction. Although the upper limit of the molar ratio of 1.30 is not a critical value, as this ratio increases, the conversion of chlorine to methyl chloride becomes less efficient, and unreacted substances in the form of hydrogen chloride increase.

JJJl: Hydrogen chloride released from the chlorination process of methane or methyl chloride is usually absorbed by water and recycled, so in this reaction carbon tetrachloride, methanol,
There is no problem with the presence of water in addition to hydrogen chloride.

Further, carbon dioxide produced as a by-product in this reaction is separated and removed from methyl chloride by a conventional method such as absorption with sodium hydroxide, alkali carbonate, or ethanolamine.

(Examples) Hereinafter, specific aspects of the present invention will be explained using Examples and Comparative Examples, but the present invention is not limited thereto.

Example 1゜ Specific surface area is 1,500 I/g, 4 books φX 6 mm
A glass tube having an inner diameter of 45 no.phi. was filled with a catalyst having a length of 450 mm and heated to 200'C. To this reaction tube, carbon tetrachloride = 56.26/hour (0,365 mol/hour), methanol: 130.9 g/hour (/!, 091 mol/hour), hydrogen chloride: 111. Og/hour (3,042 mol/hour) was supplied in gaseous form, and the reaction was carried out for 100 hours while maintaining the temperature at 200°C. After the reaction product gas is separated by water cooling in a condenser, it is bubbled in ice-cold water, and then the amount of uncondensed and untrapped gas is measured with a gas meter. Condensate, ice-cold water, gas meter person 1] The following analysis was performed on the gas.

Condensate: composition and weight of water, hydrogen chloride, methanol, chlorinated methane.

Ice-cold water: Composition and weight increase of hydrogen chloride, methanol, and chlorinated methane.

Gas meter person logas: Methanol, chlorinated methane, -oxidation carbon, carbon dioxide, dimethyl ether composition.

The amount of generated gas, which is the sum of the composition, weight, and volume of the three types of samples, was as follows.

Methyl chloride: 4.080 Morph carbon dioxide: 0.355 Methanol: 0.011 Hydrogen chloride: 0.382 Water: 4.080 Carbon tetrachloride: 0,010 As for dimethyl ether, there is a very small amount that cannot be quantified. Although detected, CH2Cl□, CH-C1,,C
No O was detected at all, and the reaction proceeded for 100 hours without decreasing the amount of gas generated by the gas meter.

Reaction rate of carbon tetrachloride: 97.2% Methanol: 99.7% Example 2゜The gas supplied to the reaction tube was reduced to 173.3 g/g of carbon tetrachloride.
hour (1,125 mol/hour), methanol: 130.9
The reaction was carried out in the same manner as in Example - except that the reaction time was changed to gZ hour (4°091 mol/hour), and the resulting gas was analyzed in the same manner.

The amount of generated gas, which is the sum of the composition, weight, and volume of the three types of samples, was 2 or less.

Methyl chloride: 4.058 mol/hour - carbon oxide: 1.09] Methanol: 0.033 Hydrogen chloride: 0,306 Water: 4.058 Carbon tetrachloride: 0,034 Note that dimethyl ether is present in very small amounts that cannot be quantified. was detected, but CH2Cl2, CHCl3, and CO were not detected at all, and the reaction proceeded for 100 hours without any decrease in the amount of gas generated as measured by the gas meter.

Reaction rate of carbon tetrachloride: 797.0% Methanol: 99.2% Comparative example Instead of using granular activated carbon as a carrier, a specific surface area of 150 m2/
The reaction was carried out under the same conditions as in the example except that spherical Al□O of 4 to 6 IIITl was used. After about 50 hours, the amount of gas generated by the gas meter began to decrease, and after 60 hours, the reaction was stopped because it was extremely low. The results of the analysis up to that point were as follows.

Methyl chloride: 2.586 mol/hour Carbon dioxide: 0.274 Methanol: 1.501 Dimethyl ether: 0.002 Hydrogen chloride: 1.560 Water: 2.586 Carbon tetrachloride:
0.089 Note that CH2Cl□, CHCL, and CO were not detected at all as in the example.

Reaction rate of carbon tetrachloride: 75.0% Reaction rate of methanol: 63.311 (Effects of the invention) According to the present invention, carbon tetrachloride can be converted into carbon tetrachloride in an extremely short time of 10 to 20 seconds at a relatively low temperature of 150 to 200°C. 95
% or more can be reacted with methanol, making it possible to convert almost the entire amount of methanol into useful methyl chloride.

Therefore, the present invention is not limited to a mere abatement treatment of harmful substances, but also provides a powerful means for producing methyl chloride.

Claims (1)

[Claims] 1. Groups IB, IIA, IIB, VIB and VI of the Periodic Table
Carbon tetrachloride, which is characterized by reacting methanol and carbon tetrachloride in a gas phase using a catalyst in which a halide or oxide of at least one element from Group IB and Group VIII is supported on activated carbon. Processing method. 2. The method for treating carbon tetrachloride according to claim 1, characterized in that the reaction between methanol and carbon tetrachloride is carried out in the coexistence of hydrogen chloride.